The game began when two people from Vaalgarn were chased through a portal to Elzeal by a mysterious woman with crystal horns, and soon allied with two people from Elzeal to chase after a man in black with plans of destroying the kingdom of humans known only as Subject 99
They eventually learned that he was working for one of the Shadow King's four elemental fiends, and the party eventually began bouncing back and forth between worlds to challenge the two major enemy forces
In Elzeal, they fought the Four Fiends as they summoned Eidolons to crush human settlements and destroy the crystals that power them, before flying north on a floating island of ancient technology to face the Shadow King himself
and in Vaalgarn, they sabotaged imperial plans while facing and toppling the massive, unstoppable machines of Project WEAPON, ultimately defeating Emperor Merovech in hand to hand combat
Throughout all this, they gradually uncovered a secret conspiracy linking the world - scientists and soldiers from both worlds, committing crimes against humanity in the name of bringing peace to their respective worlds.
After learning of the horrors she was subjected to that led her down the path of destruction, the party infiltrated her floating castle to stop her before she could bring about the apocalypse.
BUT EVEN THEN, she wasn't the true mastermind! Seven legendary weapons scattered throughout the world had been manipulating human history for millennia, in order to bring about a final event where a human would ascend to godhood, alongside the creator of the universe.
That creator, Solanima, created the cosmos and countless others before it as attempts to create a second godlike being in order to not be the only entity of its magnitude in existence.
But the power of the Crystals at the hearts of each world gathered the hopes and dreams of all of mankind and granted our four heroes the power to face Solanima in battle
to keep going, you need to use items, which heal fixed amounts of HP or ST (halved if used during a battle), or find a Sanctuary and use a tent to heal the full party
both are alien entities that only reveal the extent of their meddling in human affairs right at the end, where it turns out they've destroyed hundreds of planets that they seeded with life in order to achieve some impossible goal
I had plans originally for an Optional Bonus Dungeon at the end of the game but I cut it for time, both because I was exhausted and because I wanted to get to Lorica and Soleil sooner
And here's Solanima's three forms